KR20210030395A - Method for continuous production of polyamide powder - Google Patents

Abstract

The present invention relates to a method for the continuous production of a polyamide powder (PP) comprising at least one semi-crystalline polyamide (P). In addition, the present invention relates to the use of the polyamide powder (PP) as the polyamide powder (PP) thus obtained, the sintered powder (SP), and a method for producing a molded article by exposing the layer of the polyamide powder (PP). It is about.

Description

Method for continuous production of polyamide powder

The present invention relates to a method for the continuous production of a polyamide powder (PP) comprising at least one semi-crystalline polyamide (P). In addition, the present invention relates to the use of the polyamide powder (PP) as the polyamide powder (PP) thus obtained, the sintered powder (SP), and a method for producing a molded article by exposing the layer of the polyamide powder (PP). It is about.

Frequently today, rapid delivery of a prototype is a problem. One particularly suitable method for this "fast prototyping" is selective laser sintering (SLS). This entails selective exposure of the plastic powder in the chamber to the laser beam. The powder is melted, and the molten particles are merged and resolidified. Repeated application of plastic powder and subsequent laser exposure makes it possible to model three-dimensional shaped bodies.

The selective laser sintering method for the production of shaped bodies from powdery polymers is described in detail in US 6,136,948 and WO 96/06881.

Frequently, selective laser sintering takes too much time to manufacture a relatively large number of green bodies, and therefore, high-speed sintering (HSS) from HP or multijet fusion technology (MJF) from HP (Hewrett-Packard). It can be used to manufacture a relatively large volume of the molded article. In high-speed sintering, a higher processing speed than selective laser sintering is achieved by spraying an infrared-absorbing ink on the cross section of the component to be sintered and then exposing it to an infrared light source.

Sintered powders suitable for selective laser sintering (SLS), high speed sintering (HSS) or multijet fusion technology (MJF) are in particular polyamide powders. Various polyamide powders that can be used as sintered powders and methods for their preparation are described in the prior art. For example, polyamide powder is prepared by grinding or precipitation.

In the case of pulverization, polyamide and optional additives and/or additives are introduced into a mill and pulverized while being cooled, preferably with liquid nitrogen, to obtain a polyamide powder (low temperature pulverization).

However, the disadvantage of this method is that the polyamide powder produced by pulverization frequently has an excessively broad particle size distribution, so that the yield of the polyamide powder that can be used as a sintered powder is often very small.

When the polyamide polymer is prepared by precipitation, the polyamide and optionally additives and/or additives are typically first mixed with a solvent, the polyamide being dissolved in the solvent, optionally during heating, to obtain a polyamide solution. Is obtained. The polyamide powder is then precipitated, for example by cooling the polyamide solution, distilling the solvent from the polyamide solution or adding a precipitating agent to the polyamide solution.

The preparation of the polyamide powder by precipitation is typically carried out by what is referred to as a batchwise method, which means that the different constituent steps of precipitation are carried out successively in the same apparatus.

However, in order to obtain a large amount of polyamide powder, it is a disadvantage in this method that a high-performance device must be used, which means that the mixing of the polyamide, the solvent and any additives and/or additives is frequently insufficient. . This frequently leads to low sphericity and wide particle size distribution of the resulting polyamide powder. In addition, temperature monitoring and control in the new phase of sedimentation in the batch method is often difficult and slow.

An object of the present invention is a method for producing polyamide powder (PP), wherein polyamide powder (PP) as sintered powder (SP) is used in selective laser sintering method, high speed sintering (HSS) or multijet fusion technology (MJF). It is to provide a manufacturing method particularly suitable for. The method and sintered powder described in the prior literature The aforementioned disadvantages must be absent or greatly reduced in the method and the polyamide powder (PP) obtainable therefrom. In addition, the method should be carried out very simply and inexpensively.

The above purpose is

A method for continuously producing a polyamide powder (PP) comprising at least one semi-crystalline polyamide (P), comprising:

(a) To prepare a solution (L) containing the at least one semi-crystalline polyamide (P) dissolved in a solvent (LM), the solvent (LM) used is 30 to 60% by weight of lactam and 40 to 70 It is a mixture containing water in weight percent,

(a1) The melt (S) and the solvent (LM) by continuously supplying a melt (S) and a solvent (LM) containing at least one semi-crystalline polyamide (P) in a molten form to a mixing device (MV). Mixing in the mixing device (MV) to obtain a dispersion (D) comprising the at least one semi-crystalline polyamide (P) dispersed in the solvent (LM); And

(a2) the dispersion obtained in step a1 is continuously transferred from the mixing device (MV) to the retention device (VV) to dissolve the at least one dispersed semi-crystalline polyamide (P) in the solvent (LM) to obtain a solution Step of obtaining (L)

Including, wherein the solvent (LM), the dispersion (D) and the solution (L) are maintained at a first temperature (T1) in the step a2,

(b) the solution (L) obtained in step a is continuously transferred from the retention device (VV) to a precipitation device (FV), and the solution (L) obtained in step a is transferred in a precipitation device (FV). Cooling to a second temperature (T2) to obtain a suspension comprising the polyamide powder (PP) as a suspended phase and the solvent (LM) as a continuous phase, and

(c) obtaining the polyamide powder (PP) from the suspension (S) obtained in step b.

It is achieved by a manufacturing method comprising a.

Surprisingly, the polyamide powder produced by the method of the present invention has a high sphericity and a particularly narrow particle size distribution, and is also particularly suitable for use in laser sintering methods, high speed sintering (HSS) or multijet fusion technology (MJF). It turned out to be excellent. In addition, dissolution of at least one semi-crystalline polyamide (P) in solvent (LM) (step a) and precipitation of polyamide powder (PP) from solution (L) (step b) in three or more co-acid phase-separated apparatuses. Because it can be carried out, it is possible to optimally monitor and control the temperature in the method of the present invention.

It is also possible to use devices of a smaller volume in the method of the present invention than devices in the method carried out in the batch mode. This shortens the time required for dissolution of at least one semi-crystalline polyamide (P) in the solvent (LM) and precipitation of the polyamide powder (PP) from the solution (L). As a result, at least one semi-crystalline polyamide (P) or polyamide powder (PP) is subjected to a lower level of thermal stress, so that the molded body obtained from the polyamide powder (PP) has excellent mechanical properties, particularly a high modulus of elasticity and It has excellent tensile strength.

Further, the polyamide powder (PP) produced by the method of the present invention is obtained in a particularly high yield compared to the polyamide powder produced by grinding.

The invention is described in more detail below.

1 shows a differential scanning calorimetry (DSC) diagram including a heating run (H) and a cooling run (C).

Semi-crystalline Polyamide (P)

The polyamide powder (PP) prepared according to the invention comprises at least one semi-crystalline polyamide (P).

In the context of the present invention, "at least one semi-crystalline polyamide (P)" means exactly one semi-crystalline polyamide (P) or a mixture of two or more semi-crystalline polyamides (P).

In the context of the present invention, "semi-crystalline" means that the polyamide is in each case greater than 45 J/g, preferably greater than 50 J/g as measured by DSC according to ISO 11357-4: 2014 at 20 K/min, In particular, it means having an enthalpy of fusion _{of ΔH2 (A)} of more than 55 J/g.

In addition, the at least one semi-crystalline polyamide (P) is preferably less than 200 J/g, particularly preferably 175 J/g as measured at 20 K/min by DSC according to ISO 11357-4: 2014 in each case. It has an enthalpy of fusion _{of ΔH2 (A)} of less than, particularly preferably less than 150 J/g.

Suitable examples of one or more semicrystalline polyamides (P) are polyamides derived from lactams having 7 to 13 ring members. It is also suitable that at least one semi-crystalline polyamide (P) is a polyamide obtained by reaction of a dicarboxylic acid and an amine.

For example, polyamides derived from lactam include those derived from caprolactam, caprylolactam and/or laurolactam.

In addition, suitable polyamides are obtainable from ω-aminoalkyl nitriles. A preferred ω-aminoalkyl nitrile is aminocapronitrile, which gives nylon-6. In addition, dinitrile can react with diamine. Adipodinitrile and hexamethylenediamine are preferred here, which gives nylon-6,6. The polymerization of nitriles is preferably carried out in the presence of water and is known as direct polymerization.

When polyamides obtainable from dicarboxylic acids and diamines are used as at least one semi-crystalline polyamide (P), 6 to 36 carbon atoms, preferably 6 to 12 carbon atoms, more preferably 6 to 10 Alkanedicarboxylic acids (aliphatic dicarboxylic acids) having four carbon atoms can be used. Aromatic dicarboxylic acids are also suitable.

Adipic acid, azelaic acid, sebacic acid, dodecanedioic acid and terephthalic acid and/or isophthalic acid may be mentioned as examples of dicarboxylic acids.

Suitable amines are, for example, alkanediamines having 4 to 36 carbon atoms, preferably alkanediamines having 6 to 12 carbon atoms, in particular alkanediamines having 6 to 8 carbon atoms, and aromatic diamines such as m-xylylenediamine, di(4-aminophenyl)methane, di(4-aminocyclohexyl)methane, 2,2-di(4-aminophenyl)propane and 2,2-di(4-aminocyclo Hexyl)propane and 1,5-diamino-2-methylpentane.

At least one semi-crystalline polyamide (P) is polyhexamethyleneadiphamide, polyhexamethylene sebacamide and polycaprolactam, and nylon-6/6,6 (especially having from 5 to 95% by weight of caprolactam units) This is desirable.

Also suitable are polyamides obtainable by copolymerization of two or more of the monomers described above and below, or mixtures of a plurality of polyamides in any desired mixing ratio.

Thus, suitable polyamides are aliphatic, semiaromatic or aromatic polyamides. The term “aliphatic polyamide” means that the polyamide is formed exclusively by aliphatic monomers. The term “semiaromatic polyamide” means that the polyamide is formed by both aliphatic and aromatic monomers. The term "aromatic polyamide" means that the polyamide (P) is formed exclusively by aromatic monomers.

The following non-exclusive list includes semi-crystalline polyamides preferred for use as one or more semi-crystalline polyamides (P) in the process of the present invention.

AB polymer:

PA 4: pyrrolidone;

PA 6: ε-caprolactam;

PA 7: enantolactam;

PA 8: Caprylolactam.

AA/BB polymer:

PA 46: tetramethylenediamine, adipic acid;

PA 66: hexamethylenediamine, adipic acid;

PA 69: hexamethylenediamine, azelaic acid;

PA 610: hexamethylenediamine, sebacic acid;

PA 612: hexamethylenediamine, decanedicarboxylic acid;

PA 613: hexamethylenediamine, undecanedicarboxylic acid;

PA 6T: hexamethylenediamine, terephthalic acid;

PA MXD6: m-xylenediamine, adipic acid;

PA 6/6l: (Refer to PA6), hexamethylenediamine, isophthalic acid;

PA 6/6T: (see PA　6 and PA　6T);

PA 6/66: (see PA　6 and PA　66);

PA 6/12: (PA?6), laurilolactam;

PA 66/6/610: (PA?66, PA?6 and PA?610);

PA 6l/6T/PACM: PA 6I/6T and diaminodicyclohexylmethane;

PA 6/6I6T: (PA　6 and PA　6T), hexamethylenediamine, isophthalic acid.

At least one semi-crystalline polyamide (P) is preferably PA　4, PA　6, PA　7, PA　8, PA　9, PA　11, PA　12, PA　46, PA　66, PA　69, PA　610, PA　612, PA 613, PA　1212, PA　1313, PA　6T, PA　MXD6, PA　6/6T, PA　6/6I, PA　6/6I6T, PA　6.36, PA　6/66, PA　6/12, PA　66/6/610, PA PACM12, PA　6I/6T/PACM and two or more of the aforementioned polyamides are selected from the group consisting of copolyamides.

At least one semi-crystalline polyamide (P) is particularly preferably composed of PA　6, PA　66, PA610, PA　612, PA　6.36, PA　6/66, PA　6/6I6T, PA　6/6T and PA　6/6I. Is selected from the group.

The at least one semi-crystalline polyamide (P) is particularly preferably selected from the group consisting of PA　6, PA　66, PA　610, PA　6/66 and PA　6/6T.

Accordingly, in the present invention, at least one semi-crystalline polyamide (P) is preferably PA　4, PA　6, PA　7, PA　8, PA　9, PA　11, PA　12, PA　46, PA　66, PA　69, PA 610, PA　612, PA　613, PA　1212, PA　1313, PA6T, PA　MXD6, PA　6/6T, PA　6/6I, PA　6/6I6T, PA　6.36, PA　6/66, PA　6/12, PA　6/12, PA　6/12 /6/610, PA　PACM12, PA　6I/6T/PACM and a method selected from the group consisting of two or more of the aforementioned polyamides.

_{The at least one semi-crystalline polyamide (P) has a viscosity number (VZ (P)} ) of, for example, 70 to 350 mL/g, preferably 70 to 240 mL/g. According to the invention, the viscosity number (VZ _(P) ) of at least one semicrystalline polyamide (P) is 0.5% by weight of at least one semicrystalline polyamide (P) and 96 at 25° C. according to ISO 307:2013-08. It is measured in a solution of sulfuric acid in weight percent.

_{The at least one semi-crystalline polyamide (P) preferably has a weight-average molecular weight (M W} ) of 500 to 2000000 g/mol, more preferably 5000 to 500000 g/mol, particularly preferably 10000 to 100000 g/mol Have. The weight-average molecular weight (M _W ) is measured according to ASTM-D 4001.

The at least one semi-crystalline polyamide (P) typically has a melting point (T _{M (P)} ). _{The melting point (T M (P)} ) of the at least one semi-crystalline polyamide (P) is for example 70 to 300°C, in particular 180 to 295°C.

_{The melting point (T M (P)} ) of one or more semi-crystalline polyamides (P) is determined by differential scanning calorimetry (DSC). Typically, the melting point (T _{M (P)} ) is measured by DSC by measuring the heating run (H) and the cooling run (C). This produces, for example, the DSC diagram of FIG. 1. Subsequently, the melting point (T _{M (P)} ) is taken as the temperature at which the peak of the heating run (H) in the DSC diagram is the highest. Thus, the melting point (T _{M (P)} ) is different from the melting initiation point (T _M ^onset ) described further below. The melting point (T _M(P) ) is typically above the melting initiation point (T _M ^onset ).

In addition, at least one semi-crystalline polyamide (P) has a glass transition point (T _G(P) ). _{The glass transition point (T G(P)} ) of the at least one semi-crystalline polyamide (P) is 0 to 110°C, preferably 40 to 105°C, as measured in the dry state.

In the context of the present invention, "dry state" means that at least one semicrystalline polyamide (P) is in each case less than 3% by weight, preferably 1% by weight, based on the total weight of said at least one semicrystalline polyamide (P). %, in particular less than 0.5% by weight of solvent (LM).

With respect to the solvent (LM), the details and preferences regarding the solvent (LM) used in step a are correspondingly applicable.

_{The glass transition point (T G(P)} ) of one or more semi-crystalline polyamides (P) is determined by differential scanning calorimetry. The measurement is carried out according to the invention by measuring a first heating run (H1), a cooling run (C), and a second heating run (H2) on a sample of at least one semi-crystalline polyamide (P) (start weight About 8.5 g). The heating rate in the first heating run (H1) and the second heating run (H2) is 20 K/min. The cooling rate in the cooling run (C) is 20 K/min. A step is obtained in the region of the glass transition of at least one semi-crystalline polyamide (P) during the second heating run (H2) in the DSC diagram. _{The glass transition point (T G(P)} ) of at least one semi-crystalline polyamide (P) corresponds to the temperature at half the height of the step in the DSC diagram. Methods of measuring the glass transition point (T _G(P) ) are known to those skilled in the art.

In addition, the semi-crystalline polyamide (P) typically has a crystal point (T _{C (P)} ) of 130 to 250°C. _{The crystal point (T C (P)} ) of the semi-crystalline polyamide (P) is preferably 145 to 245°C, particularly preferably 160 to 235°C.

In the context of the present invention, the determining point (T _{C (P)} ) is likewise determined by DSC. As mentioned above, this typically involves a heating run (H) and a cooling run (C). This produces, for example, the DSC diagram of FIG. 1. Then, the crystal point (T _{C (P)} ) is the temperature at the lowest value of the crystallization peak of the DSC curve. Accordingly, the crystallization point T _{C (P)} is different from the crystallization initiation point T _C ^{onset which is further described below.} The crystallization point T _C(P) is typically less than the crystallization initiation point T _C ^onset.

Step a

In step a, a solution (L) comprising at least one semi-crystalline polyamide (P) dissolved in a solvent (LM) is prepared, wherein the solvent (LM) is 30 to 60% by weight based on the total weight of the mixture. It is a mixture comprising a lactam of 40 to 70% by weight of water.

According to the invention, "lactam" is understood as a ring amide having 4 to 12 carbon atoms, preferably 6 to 12 carbon atoms in the ring.

Suitable lactams are, for example, 4-aminobutanolactam (γ-lactam; γ-butyrolactam; pyrrolidone), 5-aminopentanolactam (δ-lactam; δ-valerolactam; pepyridone), 6-amino Hexanolactam (ε-lactam; ε-caprolactam), 7-aminoheptanolactam (ζ-lactam; ζ-heptanolactam), 8-aminooctanolactam (η-lactam; η-octanolactam; cape) Rilolactam), 9-nonanolactam (θ-lactam; θ-nonanolactam), 10-decanolactam (ω-decanolactam; capric acid lactam), 11-undecanolactam (ω-undecanolactam) ) And 12-dodecanolactam (ω-dodecanolactam; laurolactam).

Lactam may be unsubstituted or at least monosubstituted. When at least monosubstituted lactams are used, they may have one or two or more substituents on the carbon atoms of the ring.

The lactam is preferably unsubstituted.

12-dodecanolactam (ω-dodecanolactam) and/or ε-lactam (ε-caprolactam) are particularly preferred, and ε-lactam (ε-caprolactam) is most preferred.

ε-Caprolactam is the cyclic amide of caproic acid. It is also referred to as 6-aminohexanolactam, 6-hexanolactam or caprolactam. Its IUPAC name is "azepan-2-one". Caprolactam has a CAS number of 105-60-2, and its general formula is C ₆ H ₁₁ NO. Methods of making caprolactam are known to those skilled in the art.

According to the context of the present invention, the solvent (LM) used is a phonate comprising 30 to 60% by weight of lactam and 40 to 70% by weight of water, based on the total weight of the mixture.

Preferably, the solvent (LM) used is a mixture comprising 50 to 70% by weight, more preferably 35 to 45% by weight of lactam and 55 to 65% by weight of water, based on the total weight of the mixture.

In a further preferred embodiment, the solvent (LM) consists of a mixture comprising 30 to 60% by weight of lactam and 40 to 70% by weight of water, based on the total weight of the mixture.

The preparation of solution (L) consists of the following steps:

(a1) The melt (S) and the solvent (LM) by continuously supplying a melt (S) and a solvent (LM) containing at least one semi-crystalline polyamide (P) in a molten form to a mixing device (MV). Mixing in the mixing device (MV) to obtain a dispersion (D) comprising the at least one semi-crystalline polyamide (P) dispersed in the solvent (LM); And

(a2) the dispersion obtained in step a1 is continuously transferred from the mixing device (MV) to the retention device (VV) to dissolve the at least one dispersed semi-crystalline polyamide (P) in the solvent (LM) to obtain a solution Obtaining (L).

Here, the solvent (LM), dispersion (D) and solution (L) are maintained at a first temperature (T1) in step a2.

Step a1

In step a1, a melt (S) comprising at least one semi-crystalline polyamide (P) in molten form is mixed with a solvent (LM) in a mixing device (MV) to obtain a dispersion (D).

Mixing can be carried out by any method known to a person skilled in the art. In principle, the mixing device (MV) is any mixing device known to the person skilled in the art. In the context of the present invention, it is preferred to use a dynamic mixing device. Examples of dynamic mixing devices are rotor-stator and rotor-rotor dispersing devices, such as gear dispersing devices and colloidal grinders, dynamic flow mixers, in-line mixers or pumps for mixing.

In step a1, it is preferable to stir the melt (S), the solvent (LM) and the resulting dispersion (D).

Step a1 produces dispersion (D). Dispersion (D) comprises at least one semi-crystalline polyamide (P) dispersed in a solvent (LM). Thus, dispersion (D) comprises a solvent (LM) as dispersion medium (outer phase) and at least one polyamide (P) as dispersion phase (inner phase).

For example, dispersion (D) comprises from 1 to 25% by weight of at least one semi-crystalline polyamide (P) and from 75 to 99% by weight of solvent (LM), based on the total weight of the dispersion (D).

Preferably, dispersion (D) comprises 4 to 20% by weight of at least one semi-crystalline polyamide (P) and 80 to 96% by weight of solvent (LM), based on the total weight of dispersion (D).

More preferably, dispersion (D) comprises 7 to 15% by weight of at least one semi-crystalline polyamide (P) and 85 to 93% by weight of solvent (LM), based on the total weight of dispersion (D).

Accordingly, the present invention relates that the dispersion (D) obtained in step a1 is 1 to 25% by weight of at least one semi-crystalline polyamide (P) and 75 to 99% by weight of a solvent ( LM).

A melt (S) comprising at least one semi-crystalline polyamide (P) and a solvent (LM) in molten form is continuously fed to a mixing device (MV).

"Continuous feeding" of the melt (S) and solvent (LM) in the context of the present invention means that the feeding is carried out throughout the duration of step a1.

The melt (S) and solvent (LM) can be supplied by any method known to a person skilled in the art. For example, melt (S) and solvent (LM) are supplied from _{each of the separate devices V S} and V _{LM using a pump.}

The melt (S) and solvent (LM) can be fed to the mixing device (MV) at the same time from the _{respective separate devices V S} and V _LM. However, first, the solvent LM can _{be supplied from the device V LM} to the mixing device MV, and then the melt S _{can be supplied from the device V S} to the mixing device MV. It is preferable to first supply the solvent _LM from the apparatus V LM to the mixing apparatus MV, and then supply the melt _S from the apparatus V S to the mixing apparatus MV.

_{The device V LM} comprising a solvent (LM) is, for example, a container for storage.

The device V _S comprising the melt S is, for example, an extruder. Suitable extruders include all extruders known to the person skilled in the art.

After heating the solvent LM to 140 to 220°C, more preferably 160 to 200°C, it is preferable to supply it to a mixing device (MV).

The solvent (LM) can be heated by any method known to a person skilled in the art. For example, the solvent LM may be pumped from the storage container to the mixing device MV with the aid of a pump through a heat exchanger.

The melt (S) comprises at least one semi-crystalline polyamide (P) in molten form.

“Molten form” means that the at least one semi-crystalline polyamide (P) has a temperature above _{the melting point (T M (P)) of the at least one semi-crystalline polyamide (P).} Thus, "melted form" means in the context of the present invention at a temperature at which the at least one semicrystalline polyamide (P) _{exceeds the melting point (T M (P)} ) of the _{at least one semicrystalline polyamide (P) in the device V S.} It means that after being heated, it is supplied to the mixing device (MV). When at least one semi-crystalline polyamide (P) is in molten form, the at least one semi-crystalline polyamide (P) is free-flowing.

"Free-flowing" means that one or more semi-crystalline polyamides (P) _{can be transported in the device V S} , and one or more semi-crystalline polyamides (P) are _{extruded out of the device V S} and transported to the mixing device (MV). Means you can.

If the at least one semi-crystalline polyamide (P) has _{a temperature above the melting point (T M (P)} ) of the at least one semi-crystalline polyamide (P), the melt (S) is also at least one semi-crystalline polyamide (P) It will be apparent to those skilled in the art that it will have a temperature exceeding the melting point (T _{M (P) ).}

The melt (S) preferably has a temperature (T3) of 200 to 320°C, more preferably 200 to 290°C, and particularly preferably 200 to 250°C.

Accordingly, the present invention also proposes a method in which the melt (S) has a temperature (T3) of 200 to 250°C.

The melt (S) and one or more semi-crystalline polyamides (P) may optionally contain one or more additives (A).

In the context of the present invention, "at least one additive (A)" means exactly one additive or a mixture of two or more additives.

Such additives are known to those skilled in the art. For example, the one or more additives are selected from the group consisting of anti-nucleating agents, stabilizers, end group functionalizing agents, dyes and color pigments.

An example of a suitable antinucleating agent is lithium chloride. Suitable stabilizers are, for example, phenol, phosphite and copper stabilizers. Suitable end group functionalizing agents are, for example, terephthalic acid, adipic acid and propionic acid. Suitable dyes and color pigments are, for example, carbon black and iron oxide-chromium.

When the melt (S) further includes one or more additives (A), the one or more additives may likewise be present in a molten form in the melt (S). Likewise, the one or more additives (A) may be in a solid form in the melt (S).

"Molten form" in this case means that the at least one additive (A) has a temperature above the melting point (T _{M (A)} ) of the at least one additive. "Molten form" in this case means that the melt (S) has a temperature above the _{melting point (T M (P)) of at least one semi-crystalline polyamide (P).}

"Solid form" in this case means that the at least one additive (A) has a temperature below the _{melting point (T M(A)) of the at least one additive.} "Solid form" in this case means that the melt (S) has a temperature below the _{melting point (T M (P)) of at least one semi-crystalline polyamide (P).}

In the context of the present invention, and therefore always, "melt (S)" comprises at least one semi-crystalline polyamide (P) in molten form. Conversely, one or more additives (A) may be in a solid form in the melt (S).

At least one semi-crystalline polyamide (P) and optionally at least one additive (A) can be supplied to the _{device V S by any method known to the person skilled in the art.} For example, one or more semi-crystalline polyamides (P) can be supplied to the _{device V S in molten or solid form.} One or more additives (A) may optionally, likewise be supplied to the _{device V S in molten or solid form.}

When at least one semi-crystalline polyamide (P) is _{supplied to the device V S} in solid form, it can be supplied to _{the device V S} , for example in the form of pellets and/or powders. The at least one semi-crystalline polyamide (P) can then be melted _{in the apparatus V S.} This aspect is preferred.

Correspondingly, also, optionally, one or more additives (A) can be advanced _{to the device V S} in the form of a solid, such as granules or powder, preferably powder, and then optionally melted in the _{device V S.}

In addition, one or more semi-crystalline polyamides (P) may first _{be prepared directly in the device V S} , and then one or more additives (A) may optionally be supplied to the _{device V S.}

At least one semi-crystalline polyamide (P) and optionally at least one additive (A) are preferably _{combined in a device V S} to obtain a combined mixture (cM).

In the context of the present invention, "compound" is understood to mean a mixture of at least one semi-crystalline polyamide (P) and any one or more additives (A).

At least one semi-crystalline polyamide (P) and any one or more additives (A) are typically blended together in an amount present in the blend (cM) and melt (S) in which they are blended.

When the blended mixture (cM) comprises at least one additive (A), in each case a half of 90 to 99.95% by weight based on the total weight of at least one semi-crystalline polyamide (P) and at least one additive (A) Crystalline polyamide (P) and 0.05 to 10% by weight of at least one additive (A) are combined.

Preferably, in each case 95 to 99.95% by weight of at least one semicrystalline polyamide (P) and 0.05 to 5% by weight, based on the total weight of at least one semicrystalline polyamide (P) and at least one additive (A) One or more of the additives (A) are blended.

More preferably, in each case 98 to 99.95% by weight of at least one semicrystalline polyamide (P) and 0.05 to 2% by weight, based on the total weight of at least one semicrystalline polyamide (P) and at least one additive (A) % Of one or more additives (A) are combined.

In a further aspect of the invention, 60 to less than 95% by weight of at least one semicrystalline polyamide (P) and more than 5% by weight, based on the total weight of at least one semicrystalline polyamide (P) and at least one additive (A) To 40% by weight of one or more additives (A) are combined.

The sum of the weight percentages of the at least one semi-crystalline polyamide (P) and at least one additive (A) is typically 100% by weight.

At least one semi-crystalline polyamide (P) and at least one additive (A) may react with each other during compounding. Preferably, the at least one semi-crystalline polyamide (P) and any one or more additives (A) do not react during compounding.

It is understood that the weight percent of one or more semi-crystalline polyamides (P) and any one or more additives (A) relates to the weight percent before any reaction between one or more semi-crystalline polyamides (P) and one or more additives (A). Will be.

Additives may additionally be combined with one or more semi-crystalline polyamides (P) and optional one or more additives (A). Suitable additives are known to the person skilled in the art, such as talc, alkaline earth silicate metal, alkaline earth glycerophosphate metal, fillers such as glass spheres, glass fibers, carbon fibers, nanotubes and chalk, impact-modified polymers (such as ethylene- Propylene (EPM) or ethylene-propylene-diene (EPDM)), rubber or thermoplastic polyurethanes, flame retardants, plasticizers and/or adhesion promoters.

For example, in each case 0.1 to 50% by weight, preferably 0.1 to 40% by weight of the formulation, particularly preferably based on the total weight of at least one semi-crystalline polyamide (P), optional at least one additive (A) and additives Preferably, 0.1 to 20% by weight of an additive may be included.

When an additive is additionally included in the formulation, the weight percent of the at least one semi-crystalline polyamide (P) and/or any one or more additives (A) may be at least one semi-crystalline polyamide (P), any one or more additives (A) and It will be understood that it is based on the total weight of the additive.

The sum of the weight percent of the one or more semi-crystalline polyamides (P), any one or more additives (A) and the additives is typically 100 weight percent.

When the blended mixture (cM) comprises one or more additives (A), the blended mixture typically comprises one or more additives (A) in dispersed form in one or more semi-crystalline polyamides (P).

At least one additive (A) forms a dispersion phase (inner phase) and at least one semi-crystalline polyamide (P) forms a dispersion medium (continuous phase). The melt (S) typically comprises equal amounts of one or more semi-crystalline polyamides (P) and any one or more additives (A), wherein the one or more semi-crystalline polyamides (P) and any one or more additives (A) ) Are combined with each other.

Thus, when the melt (S) contains one or more additives (A), the melt (S) is the sum of the weight percent of one or more semi-crystalline polyamides (P) and one or more additives, preferably the melt (S) Typically 90 to 99.95% by weight of at least one semi-crystalline polyamide (P) polyamide (P) and 0.05 to 10% by weight of at least one additive (A), based on the total weight of.

The melt (S) is typically preferably 95 to 99.95% by weight based on the sum of the weight percent of the at least one semi-crystalline polyamide (P) and at least one additive, preferably 95 to 99.95% by weight, based on the total weight of the melt (S). At least one semi-crystalline polyamide (P) of polyamide (P) and 0.05 to 5% by weight of at least one additive (A).

The melt (S) is typically preferably 98 to 99.95% by weight, preferably based on the total weight of the one or more semi-crystalline polyamides (P) and one or more additives, based on the total weight of the melt (S). At least one semi-crystalline polyamide (P) of polyamide (P) and 0.05 to 2% by weight of at least one additive (A).

In a further embodiment, the melt (S) is typically preferably 60, based on the sum of the weight percent of the at least one semi-crystalline polyamide (P) and at least one additive, preferably based on the total weight of the melt (S). To less than 95% by weight of at least one semicrystalline polyamide (P) polyamide (P) and from more than 5% to 40% by weight of at least one additive (A).

If an additive is further included in the formulation, it will be clear that the melt (S) will also contain the additive.

Likewise, if the melt (S) contains one or more additives (A) and/or additives, it will be clear that the dispersion (D) will also contain the one or more additives (A) and/or the additives. In this case, the weight percent of the at least one semi-crystalline polyamide (P) and the solvent (LM) is the total of at least one semi-crystalline polyamide (P), the solvent (LM) and any one or more additives (A) and/or additives. Based on weight.

The sum of the weight percent of one or more semi-crystalline polyamides (P), solvents (LM) and any one or more additives (A) and/or additives is typically 100 weight percent.

Step a2

In step a2, the dispersion (D) obtained in step a1 is continuously transferred from the mixing device (MV) to the retention device (VV), wherein at least one dispersed semi-crystalline polyamide (P) is dissolved in a solvent (LM). To obtain a solution (L).

In the context of the present invention, "continuous delivery" of the dispersion (D) obtained in step a1 means that the corresponding delivery takes place throughout the duration of step a2.

The retention device (VV) used is any retention device known to the person skilled in the art. The retention device (VV) used is preferably a tubular or continuously operated stirred vessel. If a tube is used, the tube is preferably a spiral tube section.

In addition, the present invention provides a method in which the retention device (VV) is a tubular or continuously operated stirred vessel.

In case the retention device (VV) is a stirred vessel, the solvent (LM), dispersion (D) and solution (L) are preferably stirred in step a2. Suitable stirrers include all stirrers known in the art with or without partitions, such as propeller stirrers, anchor stirrers, cross-beam stirrers.

Solution LM, dispersion D and solution L are maintained at a first temperature T1 in step a2.

The first temperature (T1) at which the solvent (LM), dispersion (D) and solution (L) are maintained in step a2 is the solvent used (LM), at least one semi-crystalline polyamide (P) used, and the solvent (LM ) Depends on the concentration of the at least one semi-crystalline polyamide (P).

For example, in step a2, the solvent (LM), dispersion (D) and solution (L) are at a first temperature (T1) within 140 to 250°C, preferably 150 to 240°C, particularly preferably 170 to 220°C. maintain.

Accordingly, the present invention also proposes a method in which the first temperature T1 is maintained at a temperature of 140 to 250°C.

The temperature T1 is measured with the aid of a thermometer PT100 contained in the solvent LM, the dispersion D and the solution L, and is kept constant by a temperature control device.

The average residence time in the solvent (LM), dispersion (D) and solution in the retention device (VV) is preferably 0.1 to 10 hours, more preferably 0.1 to 5 hours.

In the retention device (VV), at least one dispersed semi-crystalline polyamide (P) is dissolved in a solvent (LM). At the end of step a2 or before step b, the at least one semi-crystalline polyamide (P) is completely dissolved in the solvent (LM). This means that the molecules of one or more semi-crystalline polyamides (P) are homogeneously and randomly distributed in the solvent (LM), and the molecules of one or more semi-crystalline polyamides (P) cannot be separated by filtration.

In one embodiment of the invention, the at least one dispersed semi-crystalline polyamide (P) is already partially dissolved in the solvent (LM) at the end of step a1 or before the start of step a2. "Partially" means that at least one semi-crystalline polyamide (P) is not completely soluble in the solvent (LM). The at least one semi-crystalline polyamide (P) is preferably 50% by weight or less, more preferably 40% by weight or less, particularly preferably 25% by weight or less, based on the total weight of the at least one semicrystalline polyamide (P). It is dissolved in the furnace solvent (LM).

However, it is preferred that at least one semi-crystalline polyamide (P) is dissolved in the solvent (LM) prior to the initiation of step a2. If before the initiation of step a2 the at least one semi-crystalline polyamide (P) is not dissolved in the solvent (LM), the at least one semi-crystalline polyamide (P) is dispersed in the solvent (LM). The at least one semi-crystalline polyamide (P) then forms a dispersion phase (inner phase), and the solvent (LM) forms a dispersion medium (outer phase).

If the dispersion (D) further comprises one or more additives (A), the one or more additives (A) can likewise be dissolved in the solvent (LM). One or more of the additives (A) may not be dissolved in the solvent (LM).

If at least one additive (A) is not dissolved in the solvent (LM), the at least one additive (A) is dispersed in a solvent (LM) comprising at least one semi-crystalline polyamide (P) in dissolved form. The at least one additive (A) then forms a dispersed phase (inner phase), and a solvent (LM) comprising at least one semi-crystalline polyamide (P) in dissolved form forms a dispersion medium (outer phase).

Any additives present in the dispersion (D) can likewise be dissolved in the solvent (LM). The additive is not dissolved in the solvent (LM) and may be dispersed in a solvent comprising one or more semi-crystalline polyamides (P) in dissolved form.

Step b

In step b, the solution (L) obtained in step a is continuously transferred from the retention device (VV) to the precipitation device (FV), and the solution (L) obtained in step a in the precipitation device is at a second temperature (T2) A suspension (S) comprising polyamide powder (PP) as a suspended phase and a solvent (LM) as a continuous phase is obtained.

In the context of the present invention, "continuous delivery" of the solution obtained in step a means that the corresponding delivery takes place throughout the duration of step b.

The second temperature (T2) at which the solution (L) obtained in step a is cooled in step b is the semi-crystalline polyamide at least one of the solvent used (LM), at least one semicrystalline polyamide (P), and the solvent (LM). It depends on the concentration of amide (P).

For example, the solution (L) obtained in step a is cooled in step b to less than 0 to 140°C, preferably from 5 to less than 135°C, particularly preferably from 10 to less than 130°C.

Accordingly, the present invention also proposes a method wherein the second temperature T2 is 0 to less than 140°C.

It will be apparent that the second temperature T2 at which the solution L is cooled in step b is less than the first temperature T1 at which the solvent LM, dispersion D and solution L are maintained in step a1.

The temperature T2 is measured with the aid of the thermometer PT100 contained in the solution L, and is kept constant by the temperature control device.

The average residence time of the solution (L) in the precipitation device (FV) is 0.1 to 2 hours, preferably 0.2 to 1.5 hours, particularly preferably 0.3 to 1 hour.

Cooling can be carried out by any method known to a person skilled in the art.

The cooling of the solution L in step b may be performed in one step or in multiple steps.

If in step b the cooling of the solution (L) is carried out in one step, step b is typically carried out in a single reactor to obtain a suspension (S). However, preferably, the cooling of the solution (L) in step b is carried out in multiple stages, more preferably in two stages.

When the cooling of the solution (L) in step b is performed in two steps, the solution (L) is cooled to a temperature (T2a) in the first step b1 to obtain a suspension (S1), and the suspension (S1) is a second Cooling to temperature (T2b) in step b2 gives a suspension (S).

Thus, in addition, in the present invention, the cooling of the solution (L) in step b is carried out in two steps, but in the first step b1, the solution is cooled to a temperature (T2a) to obtain a suspension (S1), and in the second step b2 The suspension (S1) is cooled to a temperature (T2a) to obtain a suspension (S).

The temperature (T2a) is preferably 100 to less than 140°C, more preferably 100 to less than 135°C, particularly preferably less than 100 to 125°C.

The temperature (T2b) is preferably 0 to less than 100°C, more preferably 5 to less than 100°C, particularly preferably less than 10 to 100°C.

Accordingly, the present invention also proposes a method in which the temperature T2a is less than 100 to 140°C.

In addition, the present invention provides a method in which the temperature (T2b) is 0 to less than 100°C.

When the solution (L) is cooled in two stages in step b, step b1 is preferably carried out in a first reactor (R1), and step b2 is preferably carried out in a second reactor (R2).

Accordingly, the present invention also provides a method in which step b1 is carried out in the first reactor R1 and step b2 is carried out in the second reactor R2.

In the context of the present invention, it will be clear that the term "settling device (FV)" includes one reactor or more than one reactor.

Suitable reactors in which the solution (L) or suspension (S1) can be cooled are, for example, continuously stirred tanks or tubular reactors. However, it is preferred to use a continuously stirred tank for cooling the solution L in step b.

Cooling of the solution (L) obtained in step a produces a suspension (S) comprising polyamide powder (PP) as a suspended phase (internal phase) and a solvent (LM) as a continuous phase.

The polyamide powder (PP) is described in further detail below.

The suspension (S) typically comprises from 1 to 25% by weight of polyamide powder (PP) and from 75 to 99% by weight of solvent (LM), based on the total weight of the suspension (S).

Preferably, the suspension (S) typically comprises 4 to 20% by weight of polyamide powder (PP) and 80 to 96% by weight of solvent (LM), based on the total weight of the suspension (S).

Most preferably, the suspension (S) typically comprises 7 to 15% by weight of polyamide powder (PP) and 85 to 93% by weight of solvent (LM), based on the total weight of the suspension (S).

If the solution (L) contains one or more additives (A) and/or additives, it will be clear that the polyamide powder (PP) will also contain one or more additives (A) and/or additives.

Step c

In step c, the polyamide powder (PP) is separated from the suspension (S) obtained in step b.

The polyamide powder (PP) can be separated by any method known to the person skilled in the art, such as by filtration and/or centrifugation. Thus, in step c the polyamide powder (PP) is separated from the solvent (LM) of the suspension (S).

Thus, the polyamide powder (PP) can optionally be subjected to further post-treatment. In a preferred embodiment, the polyamide powder (PP) is washed with water to remove any residue of the solvent (LM) present from the polyamide powder (PP).

In a further preferred embodiment, the polyamide powder (PP) after separation in step c is washed with water and then dried.

The drying may be a heat drying process. A preferred method of heat drying is drying, for example, in a fluidized bed supplemented with hot air, or drying under a nitrogen atmosphere and/or reduced pressure at an elevated temperature, such as 50 to 80°C.

Thus, the present invention also proposes a method in which the polyamide powder (PP) in step c is separated by filtration and/or centrifugation followed by drying.

In some cases, it may be advantageous to classify the polyamide powder (PP) after it has been separated in step c. To this end, the polyamide powder (PP) may be subjected to sieving and/or wind sifting. In general, wind sieving separates too finely from polyamide powder (PP). In general, sieving separates particles of excessive particle size from polyamide powder (PP). Only the sieving process or the wind sieving process can be performed. In addition, it is possible to perform a sieving process and a subsequent wind sieving process, or a wind sieving process and a subsequent sieving process. In addition, after the polyamide powder (PP) is separated in step c, it may be used directly as a calcining powder.

Polyimide Powder (PP)

The polyamide powder (PP) of the present invention comprises at least one semi-crystalline polyamide (P). The polyamide powder (PP) of the present invention may comprise any desired amount of one or more semi-crystalline polyamides (P).

Typically, the polyamide powder (PP) may comprise one or more semi-crystalline polyamides (P) in an amount wherein the melt (S) comprises one or more semi-crystalline polyamides (P) in step a1.

Where the melt (S) consists entirely of one or more semi-crystalline polyamides (P), the polyamide powder (PP) of the present invention also typically consists entirely of one or more semi-crystalline polyamides (P).

In the context of the present invention, "typically" means that the polyamide powder (PP) comprises 100% by weight of at least one semi-crystalline polyamide (P), based on the total weight of the polyamide powder (PP).

Also, if in step a1 the melt (S) comprises at least one additive (A) and at least one semi-crystalline polyamide (P), typically, the polyamide powder (PP) is also at least one semi-crystalline polyamide (P). And one or more additives (A). Preferably, the polyamide powder (PP) is at least one semicrystalline polyamide (P) and at least one additive in an amount in which the melt (S) comprises at least one semicrystalline polyamide (P) and at least one additive (A). It includes (A).

For example, the polyamide powder (PP) contains 95 to 99.95% by weight of at least one semi-crystalline polyamide (P) and 0.05 to 5% by weight of at least one additive (A), based on the total weight of the polyamide powder (PP). Includes.

Preferably, the polyamide powder (PP) is 98 to 99.95% by weight of at least one semi-crystalline polyamide (P) and 0.05 to 2% by weight of at least one additive (A ).

In a further embodiment, the polyamide powder (PP) is in each case 60 to less than 95% by weight of at least one semi-crystalline polyamide (P) and greater than 5 to 40% by weight, based on the total weight of the polyamide powder (PP). It contains one or more additives (A).

In this embodiment, the polyamide powder (PP) is in each case 95 to 95.95% by weight of at least one semi-crystalline polyamide (P) and 0.05 to 5% by weight of at least one, based on the total weight of the polyamide powder (PP). It contains additive (A).

In this embodiment, the polyamide powder (PP) is in each case 98 to 95.95% by weight of at least one semi-crystalline polyamide (P) and 0.05 to 2% by weight of at least one, based on the total weight of the polyamide powder (PP). It contains additive (A).

When the melt (S) further comprises an additive in step a1, it will be clear that the polyamide powder (PP) obtained in step c will also contain the additive. Typically, the polyamide powder (PP) contains the additive in an amount in which the melt (S) contains the additive.

Further, the polyamide powder (PP) may further contain a residue of the solvent (LM).

The "residue" of the solvent (LM) is, in each case, for example 0.01 to 5% by weight, preferably 0.1 to 3% by weight, particularly preferably 0.1 to 1% by weight, based on the total weight of the polyamide powder (PP). It is understood to mean the solvent (LM) of.

The polyamide powder (PP) is in each case from more than 5% to 50% by weight, preferably from 10 to 40% by weight, particularly preferably from 10 to 30% by weight, based on the total weight of the polyamide powder (PP). When containing one or more additives (A), the polyamide powder (PP) is referred to as a master batch. These master batches are typically diluted with additional semi-crystalline polyamide (P) before being used, for example, in selective laser sintering methods and/or in the production of shaped bodies. Such methods are known to those skilled in the art.

When the polyamide powder comprises an additive (A), the at least one additive (A) is typically dispersed in one or more semi-crystalline polyamides (P) in the polyamide powder (PP). At least one additive (A) forms a dispersion phase (inner phase), and at least one semi-crystalline polyamide (P) forms a dispersion medium (outer phase).

Polyamide powder (PP) typically has a melting point (T _{M (PP)} ) of 180 to 270°C. The melting point (T _{M (PP)} ) of the polyamide powder (PP) is preferably 185 to 260°C, particularly preferably 190 to 245°C.

In the context of the present invention, the melting point (T _{M (PP)} ) of the polyamide powder (PP) is determined by differential scanning calorimetry (DSC). Typically, the melting point (T _{M (PP)} ) is measured by DSC by measuring the heating run (H) and the cooling run (C). This produces, for example, the DSC diagram of FIG. 1. Subsequently, the melting point (T _{M (PP)} ) is taken as the temperature at which the peak of the heating run (H) in the DSC diagram is the highest. Thus, the melting point (T _{M (PP)} ) is different from the melting initiation point (T _M ^onset ) described further below. The melting point (T _M(P) ) is typically above the melting initiation point (T _M ^onset ).

In addition, the polyamide powder (PP) typically has a crystal point (T _{C (PP)} ) of 120 to 250°C. The crystal point (T _{C (PP)} ) of the polyamide powder (PP) is preferably 130 to 240°C, particularly preferably 140 to 235°C.

In the context of the present invention, the determining point (T _{C (PP)} ) is likewise determined by DSC. As mentioned above, this typically involves a heating run (H) and a cooling run (C). This produces, for example, the DSC diagram of FIG. 1. Then, the crystal point (T _{C (PP)} ) is the temperature at the lowest value of the crystallization peak of the DSC curve. Thus, the crystallization point T _{C (PP)} is different from the crystallization initiation point T _C ^{onset which is further described below.}

In addition, the polyamide powder (PP) has a glass transition point (T _G(PP) ). The glass transition point (T _G(PP) ) of the polyamide powder (PP) is 0 to 110°C, preferably 40 to 105°C, as measured in a dry state.

The glass transition point (T _G(PP) ) of the polyamide powder (PP) is determined by differential scanning calorimetry. According to the invention, the measurement is carried out according to the invention by first measuring a first heating run (H1), then a cooling run (C), and then a second heating run (H2) on a sample of polyamide powder (PP). (Approximately 8.5 g starting weight). The heating rate in the first heating run (H1) and the second heating run (H2) is 20 K/min. The cooling rate in the cooling run (C) is 20 K/min. Steps are obtained in the area of the glass transition of the polyamide powder (PP) during the second heating run (H2) in the DSC diagram. The glass transition point (T _G(PP) ) of the polyamide powder (PP) corresponds to the temperature at half the height of the step in the DSC diagram. Methods for such measurement of the glass transition point are known to those skilled in the art.

In addition, the polyamide powder (PP) has a sintering window (W _PP ). The sintering window (W _PP ) is the difference between the _{melting initiation point (T M} ^onset ) and the crystallization initiation point (T _C ^onset ), as will be described in more detail below. The melting initiation point (T _M ^onset ) and the crystallization initiation point (T _C ^onset ) are measured as described below.

The sintering window (W _PP ) of the polyamide powder (PP) is preferably 15 to 40 K (Kelvin), particularly preferably 20 to 35 K, particularly preferably 20 to 30 K.

In addition, the present invention provides a polyamide powder (PP) obtainable by the method according to the invention.

Due to the properties of the polyamide powder (PP) described above, the polyamide powder (PP) according to the present invention is particularly suitable as a sintered powder (SP).

Further, the present invention proposes the use of the polyamide powder (PP) according to the present invention as a sintered powder (SP).

In addition, the present invention provides a method of manufacturing a molded article by exposing the polyamide powder (PP) of the present invention to a laser.

exposure

The exposure melts at least a portion of the layer of polyamide powder (PP). The molten polyamide powder (PP) merges and forms a homogeneous melt. After exposure, the molten part of the layer of polyamide powder (PP) is cooled again and the homogeneous melt solidifies again.

Suitable methods of exposure include all methods known to those skilled in the art. The exposure is preferably carried out by means of radiant light. The radiation source is preferably selected from the group consisting of an infrared light source and a laser. A particularly preferred infrared source is a near infrared light source.

Suitable lasers are known to the person skilled in the art and are, for example, fiber lasers, Nd:YAG lasers (neodymium-doped yttrium aluminum garnet lasers) or carbon dioxide lasers.

When the radiation source used for exposure is a laser, the layer of polyamide powder (PP) is typically exposed locally to the laser beam for a period of time. This selectively melts only a portion of the polyamide powder (PP) exposed to the laser beam. When a laser is used, the method is referred to as laser sintering. Selective laser sintering is known per se to a person skilled in the art.

When the radiation source used for exposure is an infrared light source, in particular a near-infrared light source, the wavelength at which the radiation source radiates is typically 780 nm to 1000 μm, preferably 780 nm to 50 μm, in particular 780 nm to 2.5 μm.

Typically, the exposure exposes the entire layer of polyamide powder (PP). In order to melt only the desired area of the polyamide powder (PP) in the exposure, typically, an infrared-absorbing ink (IR-absorbing ink) is applied to the area to be melted.

Suitable IR-absorbing inks are all IR-absorbing inks known to the person skilled in the art, in particular IR-absorbing inks known to those skilled in the art of high speed sintering.

IR-absorbing inks typically contain one or more light absorbers that accept IR radiation, preferably near infrared (NIR) radiation. In the exposure of the layer of polyamide powder (PP), the absorption of the IR radiation, preferably the NIR radiation by the IR absorber present in the IR-absorbing ink, is caused by the layer of polyamide powder (PP) coated with the IR-absorbing ink. Causes some selective heating.

In addition to the one or more light absorbers, the IR-absorbing ink may comprise a carrier liquid. Suitable carrier liquids are carrier liquids known to those skilled in the art, such as oils or solvents.

One or more light absorbers may be dissolved or dispersed in a liquid carrier.

When the exposure is carried out by a radiation source selected from IR light sources and an IR-absorbing ink is applied, this method is also referred to as a high speed sintering (HSS) or multijet (MJF) method. Such methods are known per se to those skilled in the art.

After exposure, the layer of polyamide powder (PP) is typically reduced to the layer thickness of the layer of polyamide powder (PP) to be provided, and an additional layer of polyamide powder (PP) is applied. Subsequently, the latter is exposed again.

This first bonds the upper layer of the polyamide powder (PP) to the lower layer of the polyamide powder (PP), and furthermore, the particles of the polyamide powder (PP) in the upper layer are bonded to each other by fusion.

Exposure can be repeated.

By shrinking the powder layer, applying and exposing the polyamide powder (PP), and thus melting the polyamide powder (PP), a three-dimensional molded body is produced. It is also possible to manufacture siblings with holes, for example. Due to the fact that the non-melted polyamide powder (PP) acts as a support material by itself, an additional support material is unnecessary.

A particularly important factor in the method is the melting range of the polyamide powder (PP), referred to as the sintering window (WSP) of the polyamide powder (PP).

The WSP of the polyamide powder (PP) can be measured, for example by DSC.

In DSC, the temperature of the sample, ie the sample of polyamide powder (PP) in this case, and the temperature of the reference change linearly with time. To this end, heat is supplemented/removed from the sample and reference. The amount of heat Q required to keep the sample at the same temperature as the reference is measured. The amount of heat that is replenished/removed from the reference QR is used as the reference value.

If the sample undergoes endothermic phase conversion, an additional amount of heat Q must be replenished to keep the sample at the same temperature as the reference. When exothermic phase transition occurs, a certain amount of heat Q must be removed to keep the sample at the same temperature as the reference. This measurement produces a DSC diagram, where the amount of heat Q replenished/removed from the sample is plotted as a function of temperature T.

Typically, the measurement involves first performing a heating run (H), ie the sample and reference are heated linearly. During the melting of the sample (solid/liquid phase conversion), an additional amount of heat Q must be replenished to keep the sample at the same temperature as the reference. Then, in the DSC diagram, a peak known as the melting peak is observed.

After the heating run (H), typically, the cooling run (C) is measured. This entails linearly cooling the sample and reference, ie heat is removed from the sample and reference. During the melting of the sample (solid/liquid phase transition), due to the release of heat in the process of crystallization/solidification, a larger amount of heat Q must be removed to keep the sample at the same temperature as the reference. Then, in the DSC diagram of the cooling run (C), a peak known as the crystallization peak is observed in the opposite direction of the melting peak.

In the context of the present invention, the heating during the heating run is typically carried out at a heating rate of 20 K/min. In the context of the present invention, cooling during the cooling run is typically carried out at a cooling rate of 20 K/min.

A DSC diagram comprising a heating run (H) and a cooling run (C) is represented by, for example, FIG. 1. The DSC diagram can be used to determine the ^onset of melting (T _M onset) and the ^{onset of} _{crystallization (T C onset ).}

^{To determine the onset of} melting (T _M onset ), a tangent to the baseline of the heating run (H) at a temperature below the melting peak is plotted. The second tangent is constructed with respect to the first inflection point of the melting peak at a temperature below the temperature of the maximum of the melting peak. The two tangents are extrapolated until they intersect. The vertical extrapolation of the intersection with respect to the temperature axis represents the _{starting point of melting (T M} ^{onset ).}

^{To determine the onset of} crystallization (T _C onset ), a tangent to the baseline of the cooling run (C) at a temperature above the crystallization peak is plotted. The second tangent is drawn with respect to the inflection point of the crystallization peak at a temperature above the temperature of the lowest value of the crystallization peak. The two tangents are extrapolated until they intersect. The vertical extrapolation of the intersection with respect to the temperature axis represents the _{starting point of crystallization (T C} ^{onset ).}

The sintering window (W) is generated from the difference between the _{starting point of melting (T M} ^onset ) and the starting point of crystallization (T _C ^{onset ).} Therefore, the following equation (1) holds.

In the context of the present invention, the terms “sintering window (WSP)”, “size of sintering window (WSP)” and “ _{difference between melting initiation point (T M} ^onset ) and crystallization initiation point (T _C ^onset )” have the same meaning. Has and is used as a synonym

The present invention is described in more detail by the following examples, but is not limited thereto.

Step a

To prepare a solution (L) containing nylon-6 (Ultramid B27, BASF SE, Ludwigshafen, Germany) dissolved in a solvent (LM), the solvent (LM) in water It was a mixture of caprolactam (caprolactam content 42% by weight).

Step a1

First, a melt (S) of nylon-6 is mixed with a solvent (LM) in a dynamic mixing device (MV) (DLM/S-007 flow mixer from INDAG, D-25376 Borsplat, Germany). A dispersion (D) was obtained. The melt (S) and solvent (LM) were transferred to an extruder (D-85560 Ewe, Germany) with the aid of a three-piston membrane pump from LEWA GmbH, Leonberg, D-71229, Germany. Collin Single Screw (E16T) from Dr. Collin GmbH, Resberg, and from storage vessels were fed continuously to a dynamic mixing device (MV), respectively. Nylon-6 before the extruder was supplied in pellet form at an output of 450 g/hour, and then melted in an extruder to obtain a melt (S). The temperature of the melt (S) is 230°C. The solvent (LM) was pumped into the mixing device (MV) at an output of 4500 g/hour with the aid of a heat exchanger and the temperature was 170 to 180°C.

Step a2

Subsequently, the dispersion (D) obtained in step a1 is continuously transferred from the dynamic mixing device (MV) to the retention device (VV) (helical tube area, volume 2.5 L), wherein the dispersed nylon-6 is a solvent (LM) Dissolved in the solution (L) was obtained. The solvent (LM), dispersion (D) and solution (L) were maintained at a temperature of 175°C.

Step b

The solution (L) obtained in step a is continuously transferred from the retention device (VV) to the precipitation device (FV), and the solution (L) obtained in step a is cooled in the precipitation device (FC) to form a suspended phase. A suspension (S) comprising amide powder (PP) and a solvent (LM) as a continuous phase was obtained. The settling apparatus (FV) used were two continuously operated stirred tanks, and the cooling was carried out in two stages. In the first stirred tank (volume 2.4 L), the solution (L) is cooled to a temperature of 115° C. to obtain a suspension (S1), and in the second stirred tank (volume 6.4 L), the suspension (S1) Was cooled to a temperature below 50° C. to obtain a suspension (S).

Step c

The polyamide powder (PP) was separated from the suspension (S) obtained in step b by filtration, washing and drying.

For example, the polyamide powder (PP) of the present invention has the following particle size distribution:

D10: 8.4 μm;

D50: 36 μm; And

D90: 95 μm.

In the context of the present invention, "D10" means a particle size in which 10% by volume of particles, based on the total volume of the particles, have a size of D10 or less, and 90% by volume of the particles, based on the total volume, have a size greater than D10. Similarly, "D50" means a particle size in which 50% by volume of particles are of a size less than or equal to D50, based on the total volume of the particles, and 50% by volume of particles are of a size greater than D50, based on the total volume of the particles. Correspondingly, "D90" means a particle size in which 90% by volume of particles are of a size of D90 or less, based on the total volume of the particles, and 10% by volume of particles, based on the total volume, are of a size greater than D90.

To determine the particle size, the polyamide powder (PP) is dried with compressed air or suspended in a solvent such as water or ethanol and the suspension is analyzed. D10, D50 and D90 are measured by laser diffraction using a Malvern Mastersizer 3000. Evaluation is by Fraunhofer diffraction.

Claims (15)

A method for continuously producing a polyamide powder (PP) comprising at least one semi-crystalline polyamide (P), comprising:
(a) To prepare a solution (L) containing the at least one semi-crystalline polyamide (P) dissolved in a solvent (LM), the solvent (LM) used is 30 to 60% by weight of lactam and 40 to 70 It is a mixture containing water in weight percent,
(a1) the melt (S) and the solvent (LM) containing at least one semi-crystalline polyamide (P) in a molten form by continuously supplying the melt (S) and the solvent (LM) to a mixing device (MV) Mixing in the mixing device (MV) to obtain a dispersion (D) comprising the at least one semi-crystalline polyamide (P) dispersed in the solvent (LM); And
(a2) the dispersion obtained in step a1 is continuously transferred from the mixing device (MV) to the retention device (VV) to dissolve the at least one dispersed semi-crystalline polyamide (P) in the solvent (LM) to obtain a solution Step of obtaining (L)
Including, wherein the solvent (LM), the dispersion (D) and the solution (L) are maintained at a first temperature (T1) in the step a2,
(b) the solution (L) obtained in step a is continuously transferred from the retention device (VV) to a precipitation device (FV), and the solution (L) obtained in step a is transferred in a precipitation device (FV). Cooling to a second temperature (T2) to obtain a suspension comprising the polyamide powder (PP) as a suspended phase and the solvent (LM) as a continuous phase, and
(c) obtaining the polyamide powder (PP) from the suspension (S) obtained in step b.
Manufacturing method comprising a. The method of claim 1,
The first temperature (T1) is 140 to 250 ℃, the manufacturing method. The method according to claim 1 or 2,
The second temperature (T2) is 0 to less than 140 ℃, the manufacturing method. The method according to any one of claims 1 to 3,
In step b, the solution (L) is cooled in two stages, but in the first step b1, the solution (L) is cooled to a temperature (T2a) to obtain a suspension (S1), and in the second step b2, the suspension (S1) Cooling to a temperature (T2b) to obtain a suspension (S). The method of claim 4,
Step b1 is carried out in a first reactor (R1) and step b2 is carried out in a second reactor (R2). The method of claim 4,
The manufacturing method, wherein the temperature (T2a) is less than 100 to 140°C. The method of claim 4,
The manufacturing method, wherein the temperature (T2b) is 0 to less than 100°C. The method according to any one of claims 1 to 7,
The melt (S) has a temperature (T3) of 200 to 250 ℃, the manufacturing method. The method according to any one of claims 1 to 8,
At least one semi-crystalline polyamide (P) is PA 4, PA 6, PA 7, PA 8, PA 9, PA 11, PA 12, PA 46, PA 66, PA 69, PA 610, PA 612, PA 613, PA 1212, PA 1313, PA 6T, PA MXD6, PA 6/6T, PA 6/6I, PA 6/6I6T, PA 6.36, PA 6/66, PA 6/12, PA 66/6/610, PA PACM12, PA 6I/6T/PACM and two or more of the aforementioned polyamides, selected from the group consisting of copolyamides. The method according to any one of claims 1 to 9,
The dispersion (D) obtained in step a1 comprises 1 to 25% by weight of at least one semi-crystalline polyamide (P) and 75 to 99% by weight of a solvent (LM) based on the total weight of the dispersion (D). , Manufacturing method. The method according to any one of claims 1 to 10,
The method of manufacture, wherein the retention device (VV) is a tubular or continuously operated stirred vessel. The method according to any one of claims 1 to 11,
The production method in which the separation of the polyamide powder (PP) in step c is carried out by filtration and/or centrifugation and subsequent drying. Polyamide powder (PP) obtainable by the production process according to claim 1. Use of the polyamide powder (PP) according to claim 13 as sintered powder (SP). A method for producing a molded article by exposing the layer of the polyamide powder (PP) according to claim 13.

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